Comparison of shear bond strength of plastic and ceramic brackets

The purpose of this in vitro study is to compare the shear bond strength of various esthetic brackets used in conjunction with two different adhesive systems.

Five non-silanized ceramic brackets (Aspire Gold/Forestadent, Clarity™/3M Unitek, CLEAR/Adenta, Contour Twin/ODS, QuicKlear/Forestadent) and four plastic brackets (Aesthetik-Line®/Forestadent, Brillant®/Forestadent, Composite Clear®/ODS, Elegance®/Dentaurum) were bonded either with Transbond™ XT (3M Unitek, Monrovia, CA, USA) or with ConTec SE (Dentaurum, Ispringen, Germany) to bovine permanent mandibular incisors. Twelve specimens were tested in each group, thus, bonding 60 ceramic and 48 plastic brackets with either adhesive to a total of 216 teeth. Shear bond strength was measured in accordance with the DIN 13990-2 standard governing test methods for the entire attachment–adhesive–enamel system. The fracture surfaces resulting from shear-induced debonding were analyzed via light microscopy.

The combinations Clarity™ + Transbond™ XT, CLEAR® + Transbond™ XT, and Contour Twin + Transbond™ XT exhibited shear bond strengths of over 10 MPa. The Adhesive Remnant Index scores of the various bracket types varied widely according to the different bracket–base designs. No enamel fractures were observed.

Some bracket–adhesive combinations in this study attained shear bond strengths approaching those of metal brackets. The risk of debonding-related enamel defects is comparable with different esthetic bracket combinations. Manufacturers’ recommendations for the adhesive systems to be used with their brackets should be strictly adhered to.